胰十二指肠切除术后围手术期并发症的风险因素

目的 探讨胰十二指肠切除术后围手术期并发症的风险因素及防治措施.方法 回顾性研究北京大学第一医院2000年1月至2006年12月连续146例胰十二指肠切除术的临床资料,单因素和多因素分析影响围手术期并发症的风险因素,比较不同因素对术后并发症的影响.结果 该组病人术后围手术期并发症发生率为54.1%(79/146),死亡率为4.79%(6/146).年龄>70岁病人与70岁以下病人比较.其术后总体并发症发生率分别为66.7%及50.6%(P=0.094),其中非手术部位并发症如心肺功能不全、肺部感染等二者差异存在统计学意义(P=0.001);手术部位并发症二者无差异.术中出血>600 ml术后并发症发生率77.8%,手术部位并发症发生率71.1%,均显著高于出血<600 ml组(P值分别为0.032,0.038).术后手术部位并发症以胃排空延迟及胰肠吻合口漏最多见,保留幽门胰十二指肠切除术后胃排空延迟发生率为35.7%,较不保留幽门者显著增加(P=0.031);胰漏发生率为19.9%,由胰漏导致感染或腹腔出血并致病人死亡率为10.3%(3/29).多因素Logistic分析示胰肠吻合方式为影响术后胰漏率的独立风险因素.术前白蛋白水平,胆红素水平,术前减黄引流,手术时间,预防性应用生长抑素等均对术后并发症的发生无显著影响.结论 年龄非为手术禁忌证,但其对术后非手术部位并发症有显著影响,围手术期应重视对心肺功能的评估与监护.胰腺质地,术中失血量为术后并发症及手术部位并发症的独立危险因素.保留幽门胰十二指肠切除病人宜术中行空肠造瘘术,以术后提供肠内营养支持.根据胰管直径可采用不同的胰肠吻合方式.术前引流减黄对术后并发症的发生无显著影响.     

Risk factors and prevalence of perioperative cognitive dysfunction in abdominal aneurysm patients

BACKGROUND: Perioperative delirium is common in high-risk surgery and is associated with age, education, preoperative cognitive functioning, pre-existing medical conditions, and postoperative complications. We investigated these factors as well as lifestyle and demographic variables by using cognitive measures that were more sensitive than those used in previous studies. METHODS: Extensive medical and demographic data were collected on 102 patients between 41 and 88 years of age to identify comorbidities and lifestyle considerations preoperatively. Elective abdominal aortic aneurysm surgery was performed under combined general/epidural anesthesia with postoperative epidural analgesia. A battery of sensitive, cognitive measures was administered preoperatively, at the time of discharge from hospital, and 3 months postoperatively. Symptoms of delirium were assessed during the first 6 postoperative days using Diagnostic and Statistical Manual of Mental Disorders-4th Edition criteria. Intraoperative and postoperative data, including medications, vital signs, conduct of the surgery and anesthesia, complications, and details of pain control, were collected. RESULTS: Delirium occurred in 33% of the patients during the first 6 days after surgery. Longer duration of delirium was related to lower education, preoperative depression, and greater preoperative psychoactive medication use. Characteristics of the surgery and hospital stay were unrelated to the development of delirium. Patients who were diagnosed with delirium had lower cognitive scores during each of the three assessment periods, even when controlling for age and education. Logistic regression analysis indicated that the most powerful preoperative predictors of delirium were number of pack years smoked (P = .001), mental status scores (P = .003), and number of psychoactive medications (P = .005). CONCLUSION: A significant proportion of patients undergoing elective abdominal aortic aneurysm repair are susceptible to the development of delirium and are at risk for cognitive dysfunction after surgery. Our findings have implications for promoting long-term lifestyle changes, including smoking cessation and improved management of mental health as risk-reduction strategies.     

Long-term core outcomes of patients with simple gastroschisis

PurposeTo report the long-term core outcome set of patients with simple gastroschisis.MethodsThis was a retrospective chart review of all patients with simple gastroschisis managed at our hospital between August 2008 and July 2016. We collected all data included in the core outcome set developed for the standardization of gastroschisis outcomes reporting. We conducted a phone survey of the patients' parents using the PedsQL™ Pediatric Quality of Life Inventory, Cognitive Functioning Scale, and Gastrointestinal Symptoms Scale (GSS). Additionally, parents reported their subjective evaluation of the patients' cosmetic result and overall quality of life.ResultsThere were 124 patients included in the study. The majority (76.5%) was born prematurely at a median gestational age of 36 (range 27.6–38) weeks. At neonatal discharge (median 36 days [18–150] days) most patients were below the 10th percentile for height (81.4%) and weight (87%). Their growth, however, normalized during early childhood. Seven patients (5.6%) required at some point an operation for acute abdominal complications. One-third of patients required long-term treatment for constipation and one-third of patients required long-term treatment for gastroesophageal reflux disease (GERD). Thirty-five parents participated in the phone survey. Mean parent-reported quality of life score was better than healthy controls (87.5% vs. 82.3%, p = 0.049). Cognitive functions and gastrointestinal symptoms scores were similar to healthy controls. All patients are alive.ConclusionGrowth restriction in patients with simple gastroschisis is common at birth and during the neonatal period, but it improves during the first three years of life. Abdominal operations are rarely needed in patients with simple gastroschisis. GERD and constipation, on the other hand, are common and often require long-term medical management. The overall parent-reported quality of life of patients with simple gastroschisis is excellent.Level of evidenceLevel II.     

糖尿病患者非心脏手术围术期心血管事件的危险因素

目的 筛选糖尿病患者发生围术期心血管事件(PCE)的危险因素.方法 择期行非心脏手术的糖尿病患者500例,根据围术期是否发生PCE分为PCE组和非PCE组.记录患者一般资料和麻醉方式、麻醉时间、术中血糖、血流动力学波动情况.将组间差异有统计学意义的因素进行logis-tic回归分析,筛选PCE的危险因素.结果 79例患者发生PCE,发生率为15.8％.2组患者年龄、甘油三酯水平、高敏C反应蛋白(hs-CRP)水平、血流动力学波动情况、ECG异常比率比较差异有统计学意义(P＜0.05).logistic回归分析结果显示,甘油三酯≥1.7 mmol/L、年龄≥65岁、hs-CRP≥8mg/L和术中血流动力学异常波动≥基础值30％是非心脏手术糖尿病患者PCE的危险因素.结论 高甘油三酯、老龄、高hs-CRP水平和术中血流动力学异常波动(≥基础值30％)是糖尿病患者非心脏手术围术期PCE的危险因素.     

Risk factors for adverse outcome of newborns with gastroschisis in a Brazilian hospital

BACKGROUND/PURPOSE: The aim of this study was to determine the frequency of postoperative death and to identify factors associated with adverse prognosis in cases of gastroschisis managed in a tertiary hospital of Brazil. METHODS: A retrospective transverse study was conducted including all cases of gastroschisis managed at Instituto Materno-Infantil De Pernambuco (IMIP), Recife, Brazil, between January 1995 and December 1999 (n = 31). Prevalence risk (PR) was determined for several prenatal, intraoperative, and postoperative factors. RESULTS: Overall mortality rate was 52% (16 cases), and sepsis was the main cause of death (93.8%). Prenatal diagnosis reduced about 70% the risk of death. Preterm and low birth weight babies had about 3 times increase in the risk of death. Risk of death was increased twice among outborn babies, but there was no association with delivery route. Increase in risk of neonatal death was related to these other factors: birth-to-admission interval longer than 2 hours and birth-to-surgery interval longer than 4 hours. Prevalence risk also was greater with staged silo repair, poor clinical conditions before surgery, and when mechanical ventilation was needed. CONCLUSIONS: A high mortality rate was associated with absence of prenatal diagnosis, prematurity, low birth weight, delivery outside the tertiary center, and delayed surgery, worsening clinical conditions that preclude primary closure and increases need of mechanical ventilation. J Pediatr Surg 36:559-564.     

Risk factors and outcomes after coronary reoperation in 739 elderly patients

BACKGROUND: As second coronary artery bypass graft (CABG) operations are becoming more common in elderly patients, we conducted a retrospective analysis of risk factors for in-hospital and late outcome in patients aged 70 and over. METHODS: We reviewed records of 739 patients who underwent second CABG at age 70 or older at our institution between 1983 and 1993. Preoperative, operative, and postoperative variables were analyzed to identify predictors of in-hospital and long-term mortality. RESULTS: The mean age (+/- standard deviation) at reoperation was 74 +/- 3 years and the mean interval after primary operation was 130 +/- 55 months. In-hospital mortality was 7.6% (n = 56). Preoperative factors associated with increased in-hospital mortality were preoperative creatinine greater than 1.6 mg/dL (p < 0.001), emergency operation (p < 0.001), female sex (p = 0.012), moderate or severe left ventricular dysfunction (p = 0.049), and left main coronary disease (p = 0.045). In-hospital, actuarial survival was 75% at 5 years and 49% at 10 years. Cardiac event-free survival was 60% at 5 years and 27% at 10 years. The factors independently associated with increased late death were hematocrit (p = 0.046), diabetes (p = 0.011), peripheral vascular disease (p < 0.001), left ventricular function (p < 0.001), history of cancer (p = 0.016), preoperative nonsinus rhythm (p = 0.003), anticoagulation or antiplatelet therapy (p = 0.018), postoperative encephalopathy (p = 0.001), and postoperative stroke (p = 0.014). CONCLUSIONS: CABG reoperation can have excellent results for many elderly patients, but mortality is markedly higher when elderly patients have certain risk factors and comorbidities, alone or in combination. This information should be helpful in educating patients before they decide whether to choose reoperation.     

Risk factors for perioperative hyperglycemia in primary hip and knee replacements

Background and purpose — Perioperative hyperglycemia has been associated with adverse outcomes in several fields of surgery. In this observational study, we identified factors associated with an increased risk of hyperglycemia following hip and knee replacement.

Patients and methods — We prospectively monitored changes in glucose following primary hip and knee replacements in 191 patients with osteoarthritis. Possible associations of patient characteristics and operation-related factors with hyperglycemia (defined as glucose > 7.8 mmol/L in 2 consecutive measurements) and severe hyperglycemia (glucose > 10 mmol/L) were analyzed using binary logistic regression with adjustment for age, sex, operated joint, and anesthesiological risk score.

Results — 76 patients (40%) developed hyperglycemia, and 48 of them (25% of the whole cohort) had severe hyperglycemia. Glycemic responses were similar following hip replacement and knee replacement. Previously diagnosed diabetes was associated with an increased risk of hyperglycemia and severe hyperglycemia, compared to patients with normal glucose metabolism, whereas newly diagnosed diabetes and milder glucose metabolism disorders had no effect. In patients without previously diagnosed diabetes, increased values of preoperative glycosylated hemoglobin (HbA1c) and fasting glucose on the day of operation were associated with hyperglycemia. Higher anesthesiological risk score—but none of the operation-related factors analyzed—was associated with an increased risk of hyperglycemia.

Interpretation — Perioperative hyperglycemia is common in primary hip and knee replacements. Previously diagnosed diabetes is the strongest risk factor for hyperglycemia. In patients with no history of diabetes, preoperative HbA1c and fasting glucose on the day of operation can be used to stratify the risk of hyperglycemia.     

Pseudomonas aeruginosa bacteraemia in burns patients: Risk factors and outcomes

Introduction

We aimed to identify the risk factors for, and outcomes of Pseudomonas aeruginosa bacteraemia in adult burns patients.

Method

All adult burns patients who developed a Gram-negative bacteraemia over a period of 7 years were included. Retrospective data analysed included patient demographics, organisms cultured, antibiotic susceptibility patterns, isolation of P. aeruginosa in non-blood isolates, treatment, length of stay and mortality.

Results

Forty-three patients developed a Gram-negative bacteraemia over the study period, 12 of whom had Pseudomonas bacteraemia during the course of their admission. In eight patients (18.6%) P. aeruginosa was the first Gram-negative isolated. The only factor predicting P. aeruginosa bacteraemia as a first episode (compared to another Gram-negative) was prior isolation of Pseudomonas at other sites (wound sites, urine or sputum). Overall length of stay was less in patients who developed P. aeruginosa as a first episode, mainly because of increased mortality in this group. Prior non-blood isolates of P. aeruginosa could have correctly predicted the sensitivity pattern of the strain of P. aeruginosa organism in 75% of patients who did not receive appropriate initial antibiotics.

Conclusion

Prior colonisation with P. aeruginosa predicts P. aeruginosa in blood cultures, as opposed to other Gram-negative bacteria. Clinicians should have a high index of suspicion for P. aeruginosa bacteraemia where a septic burns patient has a prior history of non-blood P. aeruginosa cultures. Empirical antibiotic regimes based on the antibiotic-sensitivity patterns of previous non-blood P. aeruginosa isolates in each patient should be given at the time blood cultures are taken.     

Clinical characteristics and risk factors of perioperative outcomes in elderly patients with intracranial tumors

Neurosurgical Review - We aimed to study the clinical and radiological characteristics of intracranial tumors and explore the possible predictive value of these characteristics in relation to...     

Risk factors for perioperative myocardial ischemia in carotid artery endarterectomy

OBJECTIVE: To identify variables associated with perioperative myocardial ischemia in patients undergoing carotid artery endarterectomy (CEA). DESIGN: Prospective, observational study. SETTING: University-affiliated hospital operating room and intensive care unit. PARTICIPANTS: One hundred twenty-eight consecutive patients who underwent CEA during a 7-year period. INTERVENTIONS: Patients had general anesthesia with sevoflurane or isoflurane. CEA was performed by standard methods with shunting if clinically indicated. Holter electrocardiogram (ECG) monitoring was performed during surgery and 24 hours after surgery. MEASUREMENTS AND MAIN RESULTS: The incidence of perioperative myocardial ischemia was examined, and perioperative risk factors were analyzed. Nineteen patients (15%) showed significant perioperative ECG abnormalities indicative of myocardial ischemia (10 patients during surgery, 12 patients after surgery, and 3 patients both during and after surgery). Multivariate analysis showed perioperative myocardial ischemia to be significantly associated with a history of angina (odds ratio, 11.68; 95% confidence interval, 2.64-51.70) and a history of hypertension (odds ratio, 14.08; 95% confidence interval, 1.51-131.04). CONCLUSION: The data indicate that perioperative myocardial ischemia defined as an ECG abnormality does not often occur in patients undergoing CEA. However, angina and hypertension may be important risk factors warranting further investigation.     

Nutritional substrate and perioperative hypothermia

General anaesthesia causes hypothermia due to decreased metabolic rate and impaired thermoregulation. Many warming devices are in use to prevent heat loss, but little attention is paid to stimulate the body's own heat generation.All nutrients raise energy expenditure, and the highest thermic effect is ascribed to amino acids and proteins, 30–40% in the awake state. Amino acids infused during general anaesthesia exert a thermic effect that is fivefold enhanced compared with in the awake state, and may prevent postoperative hypothermia. It is still incompletely understood in which tissues and by which mechanisms nutrients stimulate heat production. However, these findings support the existence of an inhibitory action normally exerted by central thermosensors, in order to maintain oxidative metabolism within certain limits, to prevent hyperthermia. During anaesthesia, central thermosensors are silenced and hence, amino acid thermogenesis is exaggerated.The amino-acid-induced heat generation during anaesthesia predominantly occurred in extra-splanchnic tissues, most probably in skeletal muscle. It may reflect an increased protein turnover, as both protein breakdown and synthesis are energy consuming processes, known to generate heat. Possibly, amino-acid infusion provides substrates, otherwise mobilized from own tissues, needed for wound healing and immunological function. However, other cellular mechanisms may also contribute to this non-shivering thermogenesis.     

糖尿病患者非心脏手术围术期心血管事件危险因素分析

目的 探讨糖尿病患者非心脏手术围术期心血管事件的危险因素.方法 择期行非心脏手术的糖尿病患者358例,记录术中、术后恶性心律失常、心肌缺血、不稳定性心绞痛、心肌梗死、心衰[射血分数(EF)＜50％]等心血管事件,根据有无发生心血管事件分为心血管事件组和无心血管事件组,比较两组年龄、血糖、血脂、血压等,并进行多因素非条件Logistic回归分析.结果 发生心血管事件组代谢紊乱情况明显,术前合并有冠心病、高血压,年龄、心衰、微量白蛋白尿增高、糖化血红蛋白增高的发生率均高于无心血管事件组,以上危险因素均与心血管事件发生呈正相关性(P＜0.05).结论 年龄、糖尿病合并症(冠心病、心衰、肾病)是非心脏手术围术期心血管事件的主要危险因素.     

老年股骨干骨折围手术期发生心衰的因素分析

目的 :使用回归分析的方法进行老年股骨干骨折围手术期发生心衰的研究,寻找其相关危险因素,从而对其围手术心衰提出相应的临床建议。方法:对2012年7月至2017年4月期间行手术治疗的143例老年股骨干骨折患者进行回顾性分析,围手术期发生心衰组25例,男10例,女15例,年龄(77.2±12.5)岁;未发生心衰组118例,男54例,女64例,年龄(71.1±10.6)岁。调阅病例资料记录收集其受伤至手术时间、高血压病史、心脏病病史、意识障碍、术前肾功能、手术方式、手术时间、麻醉方式、围手术期液体出入量差值、围手术期疼痛评分、术后血红蛋白等资料。比较两组患者的各个因素,对结果有意义的因素再行多因素Logistic回归分析,以明确独立的危险因素。结果:单因素分析显示两组在年龄、心脏病病史、术前肾功能、围手术期液体出入量差值均有统计学意义(P0.05),多因素Logistic回归分析显示患者围手术期发生心衰的危险因素分别是为年龄[P=0.016,OR=2.789(1.208,6.439)],心脏病病史[P=0.011,OR=2.878(1.269,6.527)],术前肾功能[P=0.043,OR=2.410(1.027,5.654)],围手术期液体出入量差值[P=0.022,OR=4.215(1.230,14.439)]。结论 :年龄、心脏病病史、术前肾功能、围手术期液体出入量差值为老年股骨干骨折患者发生围手术期心衰的危险因素,围手术期应充分重视及评估这些危险因素的危害,并采用积极有效的预防和治疗措施。     

Risk factors associated with perioperative myocardial damage in patients with severe aortic stenosis

AIM: Few studies have been performed about the risk factors associated with perioperative myocardial damage in patients undergoing valve surgery for severe aortic stenosis. METHODS: To assess the prevalence of perioperative myocardial damage, we studied 103 consecutive patients with aortic stenosis. Perioperative myocardial damage (PMD) was diagnosed by both enzymatic data of peak creatine kinase iso-enzyme (CK-MB) and new appearance of electrocardiographic abnormality. PMD was noticed in 16 patients, and PMD was not noticed in 87 patients. A stepwise multiple logistic regression model was used to investigate predictors of PMD in several categorized parameters such as preoperative data, cardioplegic delivery method, and aortic clamping time. RESULTS: A multivariate analysis identified that cardioplegic delivery method, preoperative left ventricular (LV) wall thickness, and aortic clamping time were independent predictors of PMD. The incidence of PMD in the combined antegrade and continuous retrograde delivery method was significantly lower than that in antegrade delivery method (odds ratio 0.11, CI 0.02-0.61, p=0.011). The peak CK-MB value of the combined antegrade and retrograde method was significantly lower than that of the antegrade method (48+/-24 vs 71+/-50 IU/L; p=0.009). The peak lactate-dehydrogenase value of the combined method was significantly lower than that of the antegrade method (590+/-249 vs 1058+/-656 IU/L; p<0.001). The combined method decreased the incidence of PMD in patients with increased total wall thickness. CONCLUSION: Cardioplegic delivery method, LV total wall thickness, and aortic clamping time were independent predictors for PMD. Combined antegrade and continuous retrograde delivery method may be an important factor to obtain adequate myocardial protection.     

Risk factors for perioperative ischemic stroke in cardiac surgery

Objective

The purpose of this study was to evaluate the risk factors for ischemic stroke in patients undergoing cardiac surgery.

Methods

From January 2010 to December 2012, 519 consecutive patients undergoing cardiac surgery were analyzed prospectively. The sample was divided into two groups: patients with stroke per and postoperative were allocated in Group GS (n=22) and the other patients in the group CCONTROL (n=497). The following variables were compared between the groups: gender, age, carotid stenosis ≥ 70%, diabetes on insulin, chronic obstructive pulmonary disease, peripheral arteriopathy, unstable angina, kidney function, left ventricular function, acute myocardial infarction, pulmonary arterial hypertension, use of cardiopulmonary bypass. Ischemic stroke was defined as symptoms lasting over 24 hours associated with changes in brain computed tomography scan. The variables were compared using Fisher’s exact test, Chi square, Student’s t-test and logistic regression.

Results

Stroke occurred in 4.2% of patients and the risk factors statistically significant were: carotid stenosis of 70% or more (P=0.03; OR 5.07; IC 95%: 1.35 to 19.02), diabetes on insulin (P=0.04; OR 2.61; IC 95%: 1.10 to 6.21) and peripheral arteriopathy (P=0.03; OR 2.61; 95% CI: 1.08 to 6.28).

Conclusion

Risk factors for ischemic stroke were carotid stenosis of 70% or more, diabetes on insulin and peripheral arteriopathy.     

乳腺癌患者术后远处转移及其不良结局的危险因素

目的探讨乳腺癌患者术后发生远处转移及其不良结局的危险因素。 方法回顾分析2012年1月至2015年10月期间行手术治疗后发生术后远处转移67例和未发生远处转移130例的女性乳腺癌患者病例资料,随访时间截止2020年10月。采用SPSS 22.0统计软件包分析数据,单因素生存分析采用K-M法,行Log-rank检验;Cox回归模型分析乳腺癌术后转移的多因素分析。 结果脉管状态、组织学分级、肿瘤大小、淋巴结阳性数及化疗方案和靶向治疗是影响乳腺癌术后远处转移的独立危险因素（P<0.05）。67例远处转移患者死亡48例,存活19例,中位生存时间为39个月。多因素分析显示,脉管状态、肿瘤大小、临床分期、组织学分级、转移数目、Her-2状态及化疗方案和靶向治疗是影响远处转移患者预后不良的独立危险因素（P<0.05）。 结论发生脉管癌栓、肿瘤直径越大、临床分期和组织学分级越高、多部位转移、Her-2阳性是影响远处转移患者预后的独立危险因素,术后蒽环类联合紫杉类化疗可以降低远处转移率,提高患者预后。     

Risk factors for perioperative adverse events in children with myotonic dystrophy

Background:  This study was conducted to identify patient-related, surgical, and anesthetic factors that would help predict adverse events and allow for better planning of perioperative care in children with myotonic dystrophy.
Methods:  This is a retrospective chart review from a large tertiary pediatric hospital. Data were collected on demographics, disease severity, surgical procedure, and anesthetic technique. Perioperative adverse events were recorded.
Results:  Records on 27 patients having 78 anesthetics over a 17.5-year period were reviewed. The overall frequency of postoperative respiratory complications was 10%. Significant risk factors were high muscular impairment rating scale (MIRS) grade ( P  = 0.007), at least 2300 cytosine, thymine, guanine (CTG) repeats on the protein kinase gene of chromosome 19q ( P  = 0.009), a longer duration of surgery (RR = 14.0 for surgery lasting at least 1 h; P  = 0.002), perioperative morphine use (RR = 7.7, 95% CI 2.2–12.8; P  = 0.005), intubation ( P  = 0.02), and the use of muscle relaxant without reversal (RR = 15.5, P  = 0.0002). Using a multivariate risk model, only MIRS grade and the use of muscle relaxant without reversal were shown to be significant independent risk factors (RR = 24.9, P  < 0.0001).
Conclusions:  The MIRS is a statistically significant and clinically useful tool for predicting high perioperative risk. Patients with a high MIRS grade should therefore be considered for postoperative intensive care. The use of muscle relaxant without reversal was also shown to be a significant risk factor. Patients who require morphine infusions postoperatively might also be most safely managed in a high dependency unit.     

小肠梗阻术后感染性并发症危险因素分析

目的 讨论小肠梗阻术后感染性并发症的危险因素,以减少术后感染.方法 回顾分析2006年1月-2012年12月于首都医科大学宣武医院接受手术治疗的154例小肠梗阻患者的临床资料.Logistic回归分析术后感染性并发症的独立危险因素.结果 154例小肠梗阻患者接受手术治疗,术后感染率27.9％.回归分析发现,患者年龄（≥65岁）（OR 6.71,95％ CI3.15 ～ 16.33）、术中肠管破裂（OR2.71,95％CI1.19～7.25）、延迟（≥72 h）手术（OR 11.33,95％ CI 4.62 ～ 20.20）及手术时间（≥180 min）（OR 2.90,95％CI 1.26 ～9.83）是影响感染性并发症发生的危险因素.结论 术后感染是小肠梗阻术后的常见并发症.早期手术、术中轻柔操作防止肠管破裂可能是减少术后感染的有效措施.